1. Field of the Invention
The present invention relates to a display device and a driving method thereof.
2. Discussion of the Background
In general, a plurality of pixels are arranged in a matrix form in display devices, and images are displayed by controlling light intensity of each pixel according to given luminance information. Among display devices, an organic light emitting display is a display device that electrically excites a fluorescent organic material to emit light so as to display images. Since the organic light emitting display is a self-emission type, has low power consumption, a wide viewing angle, and a fast pixel response speed, it may be easy to display high-quality moving pictures. An organic light emitting display pixel includes at least one subpixel to display a desired color.
One subpixel of the organic light emitting display includes an organic light emitting element, which is typically an organic light emitting diode (OLED), and a driving transistor that drives the OLED. The driving transistor is supplied with a driving voltage from a driving voltage line to drive the OLED. In general, since driving transistors of a plurality of subpixels are commonly connected to one driving voltage line, a voltage drop may be generated due to a parasitic component existing on the driving voltage line. As a result, a driving voltage supplied to each subpixel may be different according to a position of the subpixel along the driving voltage line. When a subpixel is distant from a pad where a driving voltage line is connected to an external power supply, a driving voltage thereof may be low.
As a result, since a driving voltage of a thin film transistor may be different for each subpixel, luminance may be different with respect to the same gray. Accordingly, brightness uniformity of a screen may be deteriorated. Particularly, when high gray display is performed, a current that flows through a driving voltage line increases, which may result in increasing a voltage drop. Accordingly, a deviation of a driving voltage may increase. That is, brightness uniformity of a screen in a high gray may be further deteriorated.